This study will characterize the dispersal of an insect-borne plant virus in genetically diverse host populations and, in so doing, explore how vector-host relationships influence the propagation and maintenance of a disease epidemic. I will carry out a series of field and greenhouse experiments to explore the role of aphid infection prevalence, aphid movement and feeding behavior in determining the spread of barley yellow dwarf virus (BYDV) in genetically diverse stands of oats. The oat varieties used will either be susceptible, tolerant or resistant to infection by BYDV. Mixed stands of three different varieties of oats will be planted in the field and colonized by natural aphid populations. It will be necessary to measure aphid infection prevalence and disease incidence in the oat stands throughout the course of the epidemic. It will also be necessary to determine the spatial distribution of aphids within diseased and healthy patches within the stand. In order to determine if the acceptability of the variety changes as with its infection status, greenhouse experiments will compare feeding behavior of two aphid species on infected and uninfected plants of each variety listed above. This knowledge will grant new insight into the population dynamics of vector-borne pathogens and may in turn assist public health officials in developing more effective disease management strategies.